What would cause this colour? Smutty/Sooty gene??

My arab pony, Wildey, is a chestnut with a wide blaze and one white sock. In winter, he is a normal chestnut colour, however in summer when he sheds out he gets black dapples. Well they look more like splitches than actual dapples. He gets them mostly on his bum, more pronounced on one side than the other, always in the same place/pattern. He also gets on small dapple on the side of his neck under his mane. He also has a very faint drosal stripe, but that is a darker chestnut, NOT black like his dapples/splotches.

So my question is; what could cause this? I have been reading about the sooty/smutty gene but it says that is is normally a darkening fo the dorsal stripe and topline of the horse, and he only has a darker chestnut dorsal stripe. The black areas are either side of his bum, and the one on his neck.

Any ideas?

I'll try to find some photo's showing it.

I forgot to add, he also has a substantial amount of black hairs in his tail, the entire core of his tail is black. No black in his mane.

Pictures would definitely help but it sounds like to me that he is maybe a dark or liver chesnut. I have heard that nutritional factors can cause dappling. It is most common on fat horses. LOL.

He is very fat! Always! But it goes away for half the year. My chocolate bay horse has dapples, but they are spread over the whole bottom half of his body... Wildey is a very bright chestnut, and stays bright except for the little patches that get black hairs...

This is a picture of him without the black dappling. It's a few years old but it shows his bright chestnut colouring. I will have to look at home to find some with the dapples in.

I just had a thought. It could be "grease spots" or Bend Or spots,they are fairly common in TB that are chesnut or palomino. See the darker spots on the horses below? As for the dorsal stripe, it is probably cause by countershading. It can happen in nearly every color of horse.





Bend Or spots are also named for the TB stallion who bore them. They are random dark spots on a lighter coat, often seen on chestnuts and palominos. They vary in size, sometimes only dime-sized, and sometimes as big as an outspread palm.

They look similar, however Wildey gets a whole patch of black hairs on one side of his bum. The one on his neck looks a lot like the ones in the pictures though... Hmmm.

The splodge on his bum is pretty big, probably as high as the length of my forearm.